Officially, it’s the Metropolitan Museum of Art Costume Institute benefit, a black-tie extravaganza held the first Monday in May to raise money for the Costume Institute (a.k.a. the fashion department), the only one of the Met’s curatorial departments that has to fund itself.

Unofficially, the night’s festivities have been called many things, including “the party of the year,” “the Oscars of the East Coast” (mostly because of the star quotient and the elaborate red carpet, in which guests pose on the grand entrance stairs to the museum) and, somewhat pointedly, “an A.T.M. for the Met,” the last by the publicist Paul Wilmot.

The party signals the opening of the Costume Institute’s annual blockbuster show, and it is known for its celebrity and fashion hosts. This year, the exhibition is “Rei Kawakubo/Comme des Garçons: Art of the In-Between,” and the hosts are Anna Wintour (the Wizard of Oz for this particular event), Tom Brady, Gisele Bündchen, Katy Perry and Pharrell Williams; honorary chairwomen are Ms. Kawakubo and Caroline Kennedy, the former United States ambassador to Japan.

Why is it called the party of the year?

Ms. Wintour, the editor of American Vogue and the artistic director of Condé Nast, took over as chairwoman of the gala in 1999. Since then, she has been instrumental in transforming a local philanthropic event into the ultimate global celebrity/power cocktail: Take a jigger of famous names from fashion, add film, politics and business, and mix. It’s such a heady combo that President Trump proposed to his wife, Melania, during the gala in 2004. (In case you are wondering: No, they are not expected this year.) It is among the hardest party tickets of the year to get — and thus, intensely coveted.

Ms. Kawakubo is a 74-year-old Japanese designer who founded her label, Comme des Garçons, in 1969, and she will be only the second living designer to be given a solo show at the Met. (The first was Yves Saint Laurent in 1983.) She routinely ends up on every list of “most influential designers of the 20th century” — and, now, the 21st — in large part because she refuses to accept any of the rules that govern normal clothing design: that clothes need to be flattering, for example, or that they need to have armholes. Instead, she is interesting in challenging our ideas about what defines beauty, identity and gender. She goes where most other designers fear to tread, which is to say, into the realm of clothes that look really, really weird. (Once, when describing a collection, she said she was trying “not to make clothes.”) But she may also finally put to rest the question: Is fashion art?

Besides, know this: She also runs a multimillion-dollar international business full of lots of wearable stuff, and collaborates regularly with Nike and Speedo. If you ever see someone in a blue and white striped T-shirt with a google-eyed heart logo on the breast, that is one of hers. So are all the Dover Street Markets around the world.

How much does the gala cost?

Tickets this year are $30,000 apiece, and tables are about $275,000. The party and exhibition are sponsored, so all of the money from ticket sales goes to the Costume Institute. Last year, approximately $13.5 million was raised. In past years, there was one main corporate underwriter per show, alongside Ms. Wintour’s employer, Condé Nast. Last year it was Apple, but this year the burden is being divided among Apple, Condé Nast, Farfetch, H & M and Maison Valentino.

Of course, not everyone pays for a ticket. Brands often invite celebrities to sit at their table, and Ms. Wintour also often invites up-and-coming designers who may not be able to afford a ticket and scatters them around the event.

How many people attend?

Last year, about 600. This year, a spokeswoman for the museum said it wanted to keep it more “intimate” and “private,” so the number will be slightly lower.

So if I can afford a ticket, can I go?

Dream on. Unlike other cultural fund-raisers, like the New York City Ballet gala or the Frick Collection Young Fellows Ball, the Met gala is invitation-only, and there is a waiting list to get on the list. Qualifications for inclusion have to do with buzz and achievement (and beauty) more than money. Ms. Wintour has final say over every invitation and attendee, which means that even if a company buys a table, it cannot choose everyone who sits at its table: It must clear the guest with her and Vogue.

O.K., you’re saying I can’t go. So why should I care?

It’s reality TV at its most glamorous. Watch Selena Gomez cuddle with the Weeknd! See Future schmooze with Rihanna! Check out Chelsea Clinton kissing Diane von Furstenberg! Judge whether you approve of the outfits! (And where can you watch? We will be streaming a portion of it around 7:15 p.m. on Facebook Live at facebook.com/nytimesstyles, or on E!, starting at 7:30 p.m.)

Speaking of outfits, do attendees have to dress in theme?

It isn’t explicitly stated that attendees have to dress like the exhibition, but it is encouraged. This can backfire. In 2015, the exhibition was “China: Through the Looking Glass,” and it created some politically incorrect moments when celebrities and the designers who dressed them got their Asian references muddled. (Lady Gaga, for example, wore a Balenciaga kimonolike look, which seemed to lean toward the Japanese; ditto Georgia May Jagger in Gucci.) Last year, the show was “Manus ex Machina,” which meant everyone started thinking silver and circuitry. Almost the entire Jenner-Kardashian clan was in sparkling Balmain motherboards. Zayn Malik looked like a Versace version of the Tin Man.

All of that may pale, however, compared with what we will see this year. Why? Because, in honor of Ms. Kawakubo’s own desire to push boundaries — this has resulted in dresses that sprouted lumps and bumps on odd parts off the body, dresses that turned women into flat-packed paper dolls and dresses that turned wedding dresses into cages — guests are being encouraged to think “avant-garde.” Just ruminate on that for a moment.

Generally, it is advisable to play it safe and get really, really dressed up. Ms. Kawakubo herself almost always wears a long pleated skirt, white shirt and leather motorcycle jacket. It’s unclear if even this black-tie event will be any different.

What about celebrities?

If celebrities are invited to the gala by a brand, it is an unspoken rule that they have to wear clothes from that brand. This encourages brands to get the best stars, because they can act as something of an advertisement for a house. It is also why, whenever designers are photographed on the red carpet, their “dates” are almost always famous people. Last year, for example, Riccardo Tisci, then Givenchy’s designer, brought Madonna; Jeremy Scott brought Nicki Minaj; Michael Kors brought Zendaya.

Ms. Kawakubo is famous for not playing the celebrity game, but Lady Gaga and Ms. Perry have both worn her clothes in the past. This year, you can also expect a fair amount of Valentino, given that the company is an underwriter. For the last few years, Beyoncé has made the final entrance, but since she is about to have twins, she may well be sitting this one out. Which means the race to take her place in that power position will be something to see.

How long has this been going on?

The publicist Eleanor Lambert started the gala in 1948 as a typical philanthropic endeavor for the great and good of New York society. Pat Buckley, the wife of the conservative pundit William F. Buckley Jr., took over as chairwoman in 1979, but it has morphed into its current form only since the turn of the millennium. Ms. Wintour now oversees every detail, down to timed entrances for guests.

What happens when guests get inside?

It’s a secret! For the past two years, posting on social media has been banned after the red carpet. What I can tell you is this: There is a receiving line inside with the hosts, and guests have to file by and air-kiss them. Then they tour the exhibition on their way to the cocktail party, so they are at least theoretically forced to see the culture. After cocktails, they are called in to dinner, and there is always some form of entertainment. (Last year, it was Rihanna.) This is good, because as the red carpet part of the evening has become a giant marketing event — live streamed on a variety of sites and shown on E!, just like the Oscars — the fact that the main part of the event is private allows guests to relax and have fun.